Found in old American documentation, this circuit is current as it uses the 555 to modulate an infrared LED. Pulses are set by R1.
In this circuit the capacitor under test is charged at switch position A and then discharged...
This is a common circuit in the 1990s, when experimental FM transmitters were in vogue. The...
Using a piezoelectric sensor of the time, this circuit was found in the February 1994 issue of...